.net - Exclusive Access To Text File, To Read And Overwrite It?

I'd like to open a text file and not allow any other processes to write to it. I understand I can do this with the following FileStream:Dim fs As New FileStream(_FilePath, FileMode.Open, FileAccess.ReadWrite, FileShare.Read)

Once I have access like this I need to read all of the lines (I will use a StreamReader(fs)) and then I will need to write to the file (I will use a StreamWriter(fs)).

The problem here is that the StreamWriter won't allow me to set the append mode to false (so I can overwrite all text in the file) when I use the filestream as a parameter instead of the file path. So all text written with the StreamWriter is appended onto the text which I don't want. If I use a StreamWriter with the file path (which will let me set append to false) as the parameter instead of the filestream it will be locked out because of the FileStream FileShare. How can I still have exclusive access to read and write to the file but still be able to overwrite the existing text (append mode false)?